Crosslinking of hair thiols using cystamine

ABSTRACT

Keratinous material, such as human hair, in which disulfide linkages have been ruptured to form sulfhydryl groups can be set using cystamine.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.069,929, filed July 6, 1987, in the name of P. Siuta-Mangano entitledCROSSLINKING REAGENTS USEFUL IN TREATING HAIR.

The present invention relates to the treatment of keratinous materialsto effect improvements in permanent waving or straightening.

BACKGROUND OF THE PRESENT INVENTION

Keratinous material, which occurs in animal hair such as camel hair,mohair, wool, horsehair, cattle hair, fur and the like, and feathers,such as from poultry and, in particular, human hair consists of longpolypeptide chains crosslinked to one another by means of occasionaldisulfide linkages. The disulfide linkages act to hold the hair in adisulfide linkages permits the polypeptide chains to functionindependently, allowing for the deformation of the shape of the hairwithout elasticity. Rupture of disulfide linkages may be accomplished bythe use of various reducing agents, such as inorganic sulfides,sulfites, hydrosulfites and cyanides, mercaptans, thioglycolic acids,and various other compounds. Sulfhydryl groups are formed in place ofthe disulfide linkages.

In the cold-waving of hair, reduction of the disulfide linkages in hairis commonly performed in order to produce a permanent set, as inpermanent waving, curling, or de-kinking of hair. The shaping of hairhas conventionally been carried out by contracting the hair with areducing agent in the form of liquids, creams, or gels while the hairhas been mechanically formed into the desired new shape. The reducingcomposition is applied to the hair for a sufficient time to allowshaping to occur by the reductive disruption of the disulfide linkages.The reducing composition is then washed from the hair, and the normalresilience of the hair may then be regained by restoring thecrosslinkages either by means of oxidizing agents or by treatment withthe various crosslinking agents.

The restoration of the disulfide linkages is important in order toincrease tensile strength, as well as remove the sulfhydryl groups asreactive sites. The desired crosslinking may be obtained by oxidation,as by heating in the presence of hair or by reacting with hydrogenperoxide solution. Bromates are frequently employed as oxidizing agentsin the setting of permanently waved hair. Valuable properties may alsobe secured by the use of crosslinking agents, such as alkylene dihalidesor dihalocarboxylic acids (U.S. Pat. No. 2,739,033) or dimaleimides(U.S. Pat. No. 2,850,351). By the use of crosslinking agents, it ispossible to convert sulfhydryl linkages to cross linkages.

If permanent straightening of the hair is desired, the reducing lotionis generally applied in a thickened form such as, for instance, in acream, and evenly distributed throughout the hair by combing. The hairis combed more or less continuously and maintained in a straightenedcondition for a period of time sufficient to allow rupture of thedisulfide linkages. The shaping agent is then washed out with water andthe set is then fixed as with an oxidizing agent or a crosslinkingagent.

Many of the crosslinking agents which have been proposed heretofore arenot water-soluble and must be used in the form of emulsions. Some ofthese agents are toxic and thus difficult to employ. Others are voltaileand present a hazard to people using the same.

Other crosslinking reagents not encumbered by the difficulties of pastreagents are desirable.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, it has been found thatkeratinous materials in which disulfide linkages have been ruptured bythe action of a reducing agent can be treated to restore cross linkagesbetween keratin molecules by the application of an amount of cystaminesufficient to effect the desired treatment.

While a wide group of keratinous fiber can be treated in accordance withthe present invention, including animal hair such as camel hair, mohair,wool, horsehair, cattle hair, hog bristles and the like; and feathers,such as from chicken, duck, turkey and the like, the invention isparticularly directed to waving human hair whether in vivo or in vitro,i.e., in the form of wigs. The invention is particularly directed to"cold waving" and hair straightening systems and will be discussed inconnection therewith.

DETAILED DESCRIPTION OF THE INVENTION

The reducing agents most commonly used in cold waving hair lotions forrupturing cystine linkages are thiols or mercaptans as well as sulfitesand/or bisulfites. A number of mercaptans can only provide acceptableefficiency at high pH whereas others with a lower pK and a highionization constant can be effective at lower pH levels. For example,the ammonium salt of thiogyloclic acid can provide acceptable wavingefficiency (reduction) if the pH of the solution exceeds 9. Othercompounds such as thioglycolamides or clygol thioglycolates, sulfitesand/or bisulfites can be used at neutral or even slightly acidic pH. Thefollowing are mercaptans and thiols which have commonly been used incold waving lotions: thioglycolic acid, thiolactic acid, cysteine,thioglycerol, thioglycolic hydrazide, thioglycolamide, glycerolmonothioglycolate, beta-metcaptopropionic acid, N-hydroxyethylmercapto-acetamide, N-methyl mercapto-acetamide,beta-mercapto-ethylamine, beta-metcaptopropionamide,2-mercapto-ethanesulfonic acid, dimercaptoadipic acid, dithiothreitol,homocysteinethiolactone, cystein derivatives, and polythiol derivativesformed by the addition of cysteamine onto a maleicanhydridealkylvinylether copolymer. The sulfites and/or bisulfites whichcan be used are those normally used in hair waving such as the sodiumand ammonium salts. The amount of the reducing agent used is thatsufficient to rupture a sufficient number of disulfide bonds foreffective hair waving or hair straightening as would be appreciated byone of ordinary skill in the art.

By the breaking of the disulfide bonds to form free sulfhydryl groupspendent on the hair, the hair can be formed or shaped as desired such asby winding on rollers or pins, or combed out as in the case of hairstraightening. The breaking of the disulfide bonds is generallyaccomplished in accordance with the usual practice, which involvedapplying the reducing agent to the hair wound on curlers. Heat can beprovided at this point.

The deformed hair, while curled or straightened, is then wetted with acrosslinking composition containing the crosslinking reagent of theinvention in water or in a carrier or base such as a lotion or cream,preferably buffered. The crosslinking reagent is preferably watersoluble or made water soluble by known techniques. The carriers are ofknown types and are similar to those presently in use in waving and"neutralizing" compositions. The water or carrier desirable holds thecrosslinking reagent in contact with the hair for a period of timesufficient to effect permanent setting of the hair. Generally thecystamine is used in a concentration ranging from about 0.1% to about10% weight per volume. The crosslinking reagent is applied underconditions conductive to effecting crosslinking. A pH of between about 6and about 9 (less than that which would cause permanent breakdown of thehair protein) has been found effective for that purpose using thecompound of the invention.

The crosslinking reagent is preferably applied to the hair in a bufferedsystem, and particularly a buffered system designed to maintain the pHbetween about 6 and about 9, and preferably between about 7 and about 8.Any or a combination of alkali metal phosphates, acetates, borates andthe like which are non-reactive with the crosslinking reagent to thusdestroy crosslinking sites, can be used to maintain the pH of the hairtreated with the crosslinking composition within the range specified.Any pH effects caused by the reducing agent can be offset by thoroughwashing of the hair with water prior to the application of thecrosslinking composition.

The crosslinking composition can also contain a wetting agent orsurfactant which is non-reactive with the crosslinking reagent or thehair to destroy crosslinking sites. The surfactant can be anionic, suchas soaps. and alkyl sulfates, such as sodium dedecyl sulfate; cationicsuch as quaternary ammonium compounds; nonionic, such as glycol esters,glycerol esters, sorbitan esters, polyoxyalkalene esters,polyoxyalkalene ethers, and modified lanolin, as well as amphotericsurfactants. The surfactant is used in an amount sufficient to assist inwetting the hair with the crosslinking reagent. The amount depending onthe efficiency of the surfactant.

The crosslinking reagents can be applied to the hair alone afterreduction or in combination with a reducing agent that is compatiblewith the crosslinking reagent. The use of the single-step system allowsfor the reduction and immediate crosslinking of the sulfydryl groups.

The hair is treated for a period of time sufficient to effect thecrosslinking to provide the curl and, in some instances, tensilestrength increases desired. Illustrative times include from about 3minutes to any practical non-deterioration of the hair, upper limitthough lesser times can be used if lesser effect on the hair is desired.

The crosslinking reagent is preferably applied in aqueous solution at atemperature between the ranges of about 10° C. (50° F.) and 93° C. (200°F.). Time of treatment may vary within wide limits depending on thetemperature of the solution, the particular reducing and crosslinkingagents used, and the nature of the keratinous material being treated.

The hair can be further treated with presently used neutralizing agentsand crosslinking reagents in order to oxidize any free SH groups todisulfide linkages as would be appreciated by one of ordinary skill inthe art. The oxidizing or neutralizing chemicals used can be any of theoxidizing agents capable of restoring the disulfide linkages in the hairkeratin during the resetting stage, such as aqueous solution of hydrogenperoxide, alkali metal bromates, alkali metal perborates, urea hydrogenperoxide, sodium sesquicarbonate, etc. Rinsing alone with water mayrestore the broken linages as well, but it will be much slower.

The permanent waving system of the invention can be designed forprofessional and home application. The system and its compositions cancontain ingredients normal to such compositions. Fragrance compounds,coloring agents, thickening agents, opacifying agents, sequesteringagents, solubilizing agents, gelling agents, conditioning agents, etc.,may be added to compositions of this invention in amounts conventionallyused in hair waving and straightening compositions. Any compound whichwill react with the crosslinking reagent to remove or neutralizereactive sites thereon is preferably avoided. These ingredients arefully outlined in The Science of Hair Care, edited by Charles Zviak,Vol. 7 of a series entitled Dermatology, Marcel Dekker, Inc. 1986, whichis incorporated herein by reference.

As used herein, the term "% weight per volume" is intended to means"grams per 100 milliliters".

The present invention is more fully illustrated in the Examples whichfollow.

All neutralization (reoxidation), unless otherwise stated, was performedusing the neutralizer provided with the commercial waving lotion used inthe examples for 5 minutes. All rinsing was performed with running waterfor 2 minutes. All times are in minutes.

EXAMPLE 1

Swatches (0.5 grams; 20.3 centimeters in length) of European brownCaucasian hair wrapped around curling rods with an central diameter of1.27 centimeters were treated with a commercially available wavinglotion (Clariol® Professional Kind to Hair Perm System) for 20 minutesto rupture the disulfide bonds. These swatches were then rinsed for 2minutes with running tap water. Some swatches were treated with 10milliliters of a crosslinking solution containing about 2.5% weight pervolume cystamine crosslinking reagent in 200 millimolar sodium phosphatebuffer (pH 8.5) with 1 millimolar EDTA at a final pH of about 7.5 for 20minutes. The tresses were rinsed again under running tap water. Somesamples were further treated with the neutralizing lotion accompanyingthe commercial waving lotion in order to oxidze any free SH groups. TheClairol® Perm System control was neutralized using the neutralizerprovided with the commercial hair waving system for 5 minutes followedby a water rinse. The buffer treatment without cystamine and withoutneutralization was conducted for 20 minutes.

Hair swatches cut to 17.8 centimeters were analyzed for hanging curllength immediately after unrolling the hair swatches, after 2 hours ofgentle drying, after 1 hour of soaking in 4 liters of tap watercontaining a few drops of 29% sodium dodecyl sulfate, and after another2 hours of drying. The lengths were compared during the fifth hour,i.e., the final drying state. Curl lengths comparable to that obtainedusing the commercial hair waving system with neutralization (Clairol®Perm System) were seen with cystamine and no neutralization. Hairswatches treated with buffer alone, i.e., no crosslinking reagent, for20 minutes and no neutralization gave very little curl.

The following results, which are the average of two experiments, wereobtained. The data are reported in centimeters of hanging hair, the datafor solution being measurements made while the curl was in the solution.A reduction in length is an indication of the degree of curl.

                  TABLE 1                                                         ______________________________________                                                     Curl Length (centimeters)                                                     Wet  Dry      Solution Dry                                                    0 hr.                                                                              2 hr.    1 hr.    2 hr.                                     ______________________________________                                        Control        13.0   13.7     3.8    15.7                                    Commercial Waving                                                             System With                                                                   Neutralization                                                                Cystamine      10.4   13.0     2.5    15.7                                    Without Neutralization                                                        Buffer         13.7   13.7     5.1    16.5                                    Without Neutralization                                                        ______________________________________                                    

The above treated swatches were analyzed for luster, silky feel andcombability. Cystamine gave appearance results comparable with or betterthan the commercial lotion-treated hair or untreated hair, e.g., betterlooking curls, more luster, and more silkiness than the commerciallytreated hair swatches.

EXAMPLE 2

Example 1 was repeated with the following changes. The cystamine wasused in an amount of 5% weight per volume in 200 millimolar phosphatebuffer with 1 millimolar EDTA, final pH 7.4; one sample was treated withcystamine for 12 minutes, rinsed with water then neutralized using theneutralizer from the commercial waving system and rinsed with water; thebuffer treatment after disulfide bond severing was conducted for 12minutes, rinsed and one sample was subsequently neutralized with thecommercial neutralizer followed by a water rinse. The following resultswere obtained:

                  TABLE 2                                                         ______________________________________                                                     Curl Length (centimeters)                                                     Wet  Dry      Solution Dry                                                    0 hr.                                                                              2 hr.    1 hr.    2 hr.                                     ______________________________________                                        Control        13.2   14.7     2.5    15.7                                    Commercial Waving                                                             System                                                                        With Neutralization                                                           Cystamine      12.7   14.5     11.2   15.7                                    Without Neutralization                                                        Cystamine      12.4   14.2     3.0    15.2                                    With Neutralization                                                           Buffer                                                                        Without Neutralization                                                                       16.3   16.0     8.6    16.8                                    With Neutralization                                                                          13.7   14.7     3.8    15.7                                    ______________________________________                                    

EXAMPLE 3

Swatches of hair (as defined in Example 1) were treated on a curler. Forcontrol, a hair sample was contacted for 20 minutes with a commercialwaving lotion (Clairol® Perm System) to rupture disulfide bonds, rinsedin flowing tap water, neutralized, i.e., reoxidized, utilizing theneutralizer accompanying the commercial waving system, and rinsed. Asecond group of hair was treated with a commercial waving lotion(Clairol® Perm System) for 20 minutes to rupture disulfide bonds, rinsedin flowing tap water, treated with 10 milliliters of a crosslinkingsolution of cystamine in an amount of 2.5% weight per volume in 200millimolar sodium phosphate buffer and 1 millimolar EDTA (pH 8.5) for 20minutes (final pH 78.5), rinsed in running tap water, neutralized, andrinsed. A third set was treated the same as in the preceding procedure,except that no crosslinking reagent in the buffer was used.

The following results were obtained:

                  TABLE 3                                                         ______________________________________                                                     Curl Length (centimeters)                                                     Wet  Dry      Solution Dry                                                    0 hr 2 hr.    1 hr.    2 hr.                                     ______________________________________                                        Control        13.3   14.0     2.6    14.6                                    Commercial Waving                                                             System, Neutralized                                                           Cystamine, Neutralized                                                                       12.7   14.0     2.5    14.6                                    Buffer, Neutralized                                                                          12.7   14.0     3.2    14.6                                    ______________________________________                                    

Single tagged hair strands were analyzed for tensile propertiesincluding break point, maximum elongation before break, and total work.A decrease of from 2% to 12% in tensile properties was noted over thecontrol. Optimization of the system may avoid these decreases.

What is claimed is:
 1. A process for treating keratinous material inwhich disulfide linkages have been ruptured to form sulfhydryl groups bythe action of a reducing agent which comprises contacting saidkeratinous material with cystamine in a carrier at a pH in the range offrom about 6 to about 9 to crosslink sulfhydryl groups.
 2. The processas claimed in claim 1 wherein the keratinous material is human hair. 3.The process as recited in claim 1 wherein the cystamine is used in anamount effective to crosslink an amount of sulfhydryl groups sufficientto set the keratinous material.
 4. The process as recited in claim 1wherein the cystamine is used in a concentration ranging from about 0.1%to about 10% weight per volume.
 5. A process which comprises treatinghair with a reducing agent until a substantial portion of disulfidegroups of the hair are converted to sulfhydryl groups and, whilemaintaining the hair in a fixed position, contacting the hair withcystamine in an amount and under conditions sufficient to set the hair.6. A process which comprises contacting human hair, while the hair ismechanically maintained in a suitable condition of curl, with an amountof a reducing agent capable of rupturing disulfide linkages in the hairand a hair setting amount of cystamine.
 7. The method of claim 6 whereinthe human hair is simultaneously contacted with the reducing agent andcystamine.